Japanese Unexamined Patent Publication No. JP2006-106680 discloses an optical module having an optical receptacle structure. The optical module includes a stub ferrule (fiber stub), a sleeve, a holder, and an adapter. The stub ferrule guides laser light to an optical fiber connected to the optical module. The sleeve holds the stub ferrule and an optical connector ferrule of the optical fiber connected to the optical module. The holder holds the stub ferrule and the sleeve fixed thereto. The adapter connects the holder with the optical module. Japanese Unexamined Patent Publication No. JP2008-151956 discloses an exemplary optical adapter. Japanese Unexamined Patent Publication No. JP 2013-50512 discloses an exemplary optical transceiver.